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Topic: Racer Resurrection (Read 46513 times)

Spacers are finished on the front end. I’m getting better with the lath, got the spacers to within 0.01mm of my goal - WOOT! I will admit I lapped down to the end. In the end it’s a 9mm spacer at the hub, and a 7mm at the fork leg. This should wrap up all the fabrication on the front end. Just need to rebuild the shocks and Finnish truing the rim - can I tell you how much I hate truing the rim.

Look at that!

For the rear bar, I didn’t see an offset of any significance with the rear bar. So I figured a small bend to better angle the bar and keep it flat against the break would be good. Looks like I’ll have plenty of clearance for the rear tire, so no rubbing issues.

New rear torque bar on top, old bar below. Old and new front, and spacers as well.

I also started playing around with some epoxy to make a new fender for the rear. Brought out the exotic materials from a previous project. Should be worth 2hp. Also making one from fiberglass - if I understand correctly I can’t use carbon kevlar in AHRMA.

Fork rebuilding over the weekend. Boy, I don’t think they were touched since they were pressed into service. What a mess.

Draining the forks was simple enough. But didn’t get a lot out - maybe 30cc of oil. The tare down reveled a lot of sludge, but thankfully not a lot of striped or worse out parts. Everything cleaned up and went back together with little drama. Except for removing the old seals. What a PITA.

As part of the rebuild, I made a simple fork oil level gauge. Section of aluminum tubing, section of aluminum hose, and an epoxy syringe. Dried out an aluminum plate and put two locking colors on the tube. Vualá!

I picked up 4 seals, two ball bearings and sprints and o-rings. And a pare of new stickers.

I suspect I’ll have some changes to make in the set up. But I need to get the bike complete, and my gear unhand before I start doing suspension tuning. Until then, the new seals should keep the oil off the floor.

I put about 235cc’s into the fork. After pumping the fork up and down to get the oil circulating, and get the air out, I sucked the oil level down to 15mm below the fork tube top, with the fork fully compressed. It looked like I sucked about 1cm to 1.5cm from each tube. I started with a 30 weight fork oil. Probably to stiff, but it’s a place to start.

I used ATF for a long time then switched to 15 or 20 wt fork oil. Can't remember what I had last. I've been wanting to install gold valve emulators from Race Tech. Maybe over the off season as the fork seals have been leaking for some time.

Took a little time off for the holidays, but its back to schedule now.

To revisit an old topic from post #63. The aluminum rims I got from eBay are no longer going to be used. Countless hours later, and they still refuse to become round and true.

So a set of Excel rims were ordered. I can not tell you how easy it was to build these rims. I had to send my hubs off to Buchanan Spokes for the rims to be drilled. The hole process took about two weeks from shipping them out to getting them back. Worth every penny.

And a video

A new axle is being created this week. So the front end should be finished up by the end of the month. Then it’s on to the engine, and I suspect some work will be needed on the pipes.

I swear I’m making progress still. It’s just bit to cold to get out in the shop. So I’v occupied myself with internal engine bits.

I’m lucky that the bike came with 3 cranks. 2 in serviceable, if not usable condition. And the third is the one that wrapped the connecting rod around itself. Need to keep the other two usable until Paul perfects his new crankshaft process. ;-)

Crankshaft with spun connecting rod

Backup Crankshafts

I’m a bit curious about the center bearing between the two crankshafts.

The crank that was in the engine has the smooth center bearing. I have another one with the same bearing and one where the center bearing has a groove. Is there a fundamental difference? Or am I seeing the affect of an early and late part?

My wife splurged and bought me an aluminum removal tool for my birthday. Very excited! So I had to try it out and removed some aluminum. Lots of fun, and just a little scary. It helps that my wife is a jeweler, so as much as this is a new tool for me. She gets to use it as well. No matter, it was still fun removing a little metal.

New Toy!

Didn’t get to radical with my cutting. Followed the recommendations in the “Tuning Up for Competition” manual. Widening the exhaust port 2mm on each side, and widening the transfer ports 3mm. The transfers were a bit tricky, trying to keep the angle of the back of the port directing the flow. Guess we’ll see how I did eventually.

Aluminum!

Before & After

The cylinders are off at Millennium now having the chrome “removed”. Then fitted for the new pistons and Nickel’d. They seem like a very good group and we took some time to talk about the bike and modifications. Correctly calling into question my sanity for turning a Bridgestone into a 200GP bike.

This weekend should see me CCing the heads in preparation for cutting them down. Lets just hope is warms up in the next couple of weeks to I can get back to the shop. Because I’m not sitting there in 34° to try to precisely skim off the head.

Burette

After that its gathering gaskets, rebuilding the carburetors and sorting out an ignition.

For simplicity, I’ll follow the Dyna S points replacement guide. So that should be relatively uneventful.

Anyone have recommendations for carb rebuild kits, and gaskets? Does anyone have our pattern that provides different thickness cylinder base gaskets?

Re: center bearings - you're seeing early and late versions, the smooth one being the early version. Diameters and width are the same. Apparently, the early ones rotated in the bore, so they pinned them in later units. That would be the best setup, but you'd have to machine the case for the locating pin. I suspect you could use Loctite Bearing Retainer on the early version and be OK if necessary, but pinning it would be more reliable.

I always wanted one of those angle grinders, but never bit the bullet. Congratulations!

The Dyna S needs a third wire (+12V) to the trigger units that the points don't have, so you have to add it to the harness to the alternator/ignition unit.

I'm assuming that what you mean by the smooth bearing you were referring to the one without the groove? As Karl was indicating one has a locating pin and one a groove. I thought the bearings with a grove and no locating pin are the early bearings. They get lubricated by the oil/gas mixture thru the hole in the transfer port and the mixture makes it's way around the groove. At least that's how I picture it. The later bearings which it looks like you have two, are located on a pin so that the hole in the transfer lines up with one of the holes in the bearing case. Maybe this was better for lubrication? I went back and looked at your earlier photos in the beginning of the post. It looks like you have an early set of cases as I don't see a locating pin in the upper half of the cases. I have had a good machinist add the hole to a set of cases. I also noticed that the RH profile pic shows the lack of a post for an idle gear and it looks like the oil port has been plugged to the upper left of the rotary valve cover. I've seen many different cases. I'll have to double check and see which ones in particular but some have no provision for the idle gear post, some have a plug that can be removed and you can add the post and the others have the post.

The difference being that the ones with no post are motors that the ignition spins at half speed. The motors with extra idle gear, the ignition spin at full speed. That is gonna make the difference on how you set up your ignition. If I remember the half speed ignitions fire at 90 deg and the full at 180 deg. The first ignition I set up only fired correctly on one cylinder because it wasn't triggering to fire the other cylinder at the right time.

As to where to get gaskets and stuff? I just got some base gaskets in aluminum from Cometic. I had base gaskets done there awhile ago (that I still have because I didn't like them) so I had them modify the file to be just a basic square on the outside with the 175 porting layout in the center. This way I can modify them to fit and I can trim them to fit a 200 case/port layout if I need. I got them in .025", .032" and .040". The 22mm carbs are pretty much the same as Kawasaki A1 250. I think there are kits available out there somewhere. I also had case cover gaskets done at Cometic so they should have the pattern. The part numbers for the aluminum base gaskets are B1055SP1025A, B1055SP1032A and B1055SP1040A. They cost me about $7-8 each. I attached a copy of the base shim I use now. The Cometic ones are just square and need to be trimmed to fit.

My description of the bearings was confusing to say the least. Paul's description is correct, the one with the groove is the early version, the one with the pin is the later. I incorrectly called the one without the pin but with a groove the smooth one vs. one with a locating pin hole. Paul is also correct, the change to add the pin may have been to assure better alignment of the outer race with the lube feed hole in the crankcase; I had always assumed it was to keep the bearing race from spinning as many early Yamahas had that problem.

If you have a choice, it's better to use the crankcase/alternator combination that runs the alternator at full engine speed. It's easier to set up points or convert to electronic ignition since it triggers at 180°. You can put the 1/2 speed setup on a later crankcase by leaving out the idler and using the larger alternator gear, but you can't put the later one on the early crankcase since there's no place for the idler.

An interesting note on the carburetors - the A1 carburetors have the same slide, needle, needle jet and idle jet as the BS 175 racer carbs. I always ran Mikunis, the A1 carbs were a real help since they have the enricheners, making cold starts much easier.

I looked at your picks again. It's funny to see the crazy stuff Bridgestone did. The early crank with the groove bearing has connecting rod bearings that have two rollers next to each other. These have bronze cages. Super trick. I'm sure they were too expensive and they went to a more standard type of bearing. The earlier cranks also have center bearings with bronze cages. The later type are all steel. One of these days I'm gonna try one of the early bronze type center bearings.

Just a note to check the barrels when you install them to the cases. There is usually a fair amount of flashing from the process and the cylinders might be tight going into the case. You might have to file around the spigot until the cylinder fits smoothly into the case.

Things continue to move in fits and starts. But I’ll take any progress at this point.

Cylinder HeadsSpent some time in the kitchen - or as I like to call it the mad scientist lab - the other week, playing with my new toy. It’s a 50ml burette and has plenty of capacity our little heads. Filled I can get 3 or 4 “test” fills into the head. A simple plexiglass plate, with a hole made up the rest of the lab equipment. Smeared with a little grease between the plate and head, and its off to races we go.

I took a cheep vice grip plier from harbor freight. Drilled a hole in the locking link, and bolted it to dial indicator holder and magnetic base. It made a good solid head stand, and allowed me to position the head with a slight angle upward toward the hole in the plexiglass plate.

For the CC-ing, I used an NGK B8HN plug. After all it’s the recommended plug in the manual, and filled burette with alcohol. I did 4 tests fills in each head. The average was 11.8cc. With the difference between each test being more my reading against the lines in the burette, or a slight over pour.

Custom Head Clamp

11.8 CCs of Alcohol

The next task is to shave the heads to raise the compression. The manual recommends 1.5mm to 2mm or, 0.059” to 0.078”. To do that I’ll need to start by making up a jig to hold the head in the lathe. I’m thinking of a simple mild steal rod with the end turned down to fit up into between the fins and drilled to 14mm. Then use a 14mm bolt to “bolt” the head to the jig.

If anyone has any thoughts on a better way to do this..

On to the cylinders

The cylinders came back from Millennium, and boy do they look good. Perfect with a nice cross-hatch.

After a good initial chat when I sent the cylinders in, going back and forth between a piston clearance of .0020” or .0025”. We settled on .0020”. They also cleaned up the flat ends. One cylinder had a lot of markings on the deck from the aluminum gasket - over tightening perhaps?

Started to check the ring gap. Could use a little guidance here, not sure where I should be netting out as far as how wide the gap should be. I read .015” or .381mm with nice steady resistance when I draw the feeler gauge out.

Ring Gap

To Paul’s point above, some work needs to be done to the cylinders where they insert into the case. Both the smoothness of the port opening as well as the ports matching to the case. That should be the easy part.

On the topic of running head gaskets. I'm debating running one, or getting the lapping compound out and attack the cylinder deck and head. A good flat lapped surface would allow me to run without a head gasket. It’s appealing but I don’t fully understand the drawbacks. One benefit is that it would effectively “raise” the cylinder ports in relation to the piston. And if I understand it correctly, provide better results in top end performance. Providing we get the compression ratio increased correctly. Then use the thickness of the base gasket to tune the final deck height and compression ratio.

A summary of Karl’s setup: He machined the head down .035", and did some machining to the chamber to net out at 7.2cc and with a compression ratio around 13:1. He is running with the stock head gasket.

I'd certainly do a dry build before machining the cylinders. You've happened upon a great way of increasing your port timings with very little work. The timings I run are around 134 degrees for transfer ports...and around 196 degrees for exhaust.Dry build and see what yours come out at...but you'll need quite a few more than standard if you want it to rev.

You can set the squish, such as it is with standard heads, by turning them so the combustion chamber sits inside the cylinder.This is a good thing: It locates the head guaranteed centrally...it makes for a better seal.

We have a mandrel for skimming heads... basically a bar machined true with a 14mm sparkplug thread machined on the end.Very often factories machined the heads this way so it usually runs true.Just mount the head and turn it down from the outside in until you're at ( if 175) 50mm etc.

Al, there was a miscommunication, I took .035 off the top of the cylinders to take advantage of the automatic increase in port open time from the shorter piston.

Re: head machining; my brother has a commercial tool that is just a 1" round bar stock with a 14mm spark plug thread on one end like Vinny described. We used that to mount the heads in the lathe. It was inexpensive; I'll ask where he got it.

As Vince said about the dry build. Very important. I sent a set a cylinders back to Millennium for repair. These had already been plated by them previously. When I put the first cylinder on with my normal base shim, the piston hit the head. They apparently skimmed the cylinders on the base to square them up. I remember reading on their disclaimer something about that. Just didn't think it would be too much. I had to use the thickest base shims I had and some heads with a minor cut with about 8cc trap (with spark plug). Gotta go back and figure what base shim I will need since I usually run the piston 1mm down from the top of the cylinder.

I just had about four different sets of heads machined for dowel pins to locate the heads. I couldn't use any of them because the piston stuck out of the bore enough to hit and the thickest base shim didn't allow for enough clearance.

I didn't measure them before I sent them so I'm not sure. These were also done by them once before. I measured them now and they appear to be around 80mm and a standard cylinder was around 82mm. When I pull it back apart to figure out what base shims I will need, I'll get an exact measurement. The thickest base shims I had were from Cometic and supposed to be .040". They measured out to .037" and the normal ones I use are .032". I was able to get a squish of around .87/.88mm so I went with that.